Field of the Invention
The present invention is related to lightweight railway cars and more particularly relates to such cars having side sills and body bolsters which are light in weight, with the side sills reinforced to minimize local buckling.
Because of the overall size limitations within which a loaded railway car must fit, and because of the railway clearances and the configuration of conventional side-loading equipment available for loading containers onto railway cars, only a limited amount of volume is available within which the side sill structures of a container-carrying railway car may be constructed. Nevertheless, the side sills must have sufficient strength to support vertical bending loads applied when the car is laden, and to resist torsional and axial stresses resulting from the loads applied during travel of a laden car. Nevertheless, the weight of the side sill structures must be kept to a minimum in order not to limit the revenue-producing load which may be carried on such a car equipped with conventional trucks. While a thin-walled box beam structure can provide, theoretically, the required strength to support the expected vertical loading, the compressive axial loading to which the side sills of a railway car may be subjected, as a result of the normal operation of a railroad train, is likely to result in localized buckling of the thin metal of such a box beam structure, ultimately resulting in complete failure of the side sills, unless reinforcement is provided. Conventional internal web reinforcing structure for thin-walled box beam structures expected to be subjected to bending, axial compression, and torsional stresses is undesirably heavy and costly to assemble for use in such railway cars.
Since cargo containers are placed between the side sills, structural interconnection between the top edges of the side sills is prevented, and the side sills must, therefore, have sufficient torsional rigidity to prevent failure when such a container-carrying railway car is laden, particularly if two containers, such as 20-foot containers, are carried on such a car end-to-end, applying vertical loading midway between the supporting trucks of the car. The side sills of such a car must, then, have ample strength to resist torsion as well as vertical loading without being excessively heavy.
In accordance with the present invention, lightweight but strong side sills are each constructed of a thin metal outer plate to which is welded a thin inner channel that is provided with a plurality of spaced apertures along its length. A plurality of short transversely extending strengthening rings or tubes are welded to the outer plate and to the peripheries of the apertures in the channel to provide a rigid box beam side sill in which localized warping and buckling during normal operation is prevented by the interconnection of the opposite vertical faces of the side sill at the locations of the tubes. The weight of the thin-walled side sills is significantly less than that of conventional closed box beam construction using sheet material thick enough to accept the same loading without reinforcement. Additionally, the weight of material removed from the channel member to form the openings compensates at least partially for the weight of the tubes, and may be greater than the weight of the tubes, thus further reducing the overall weight of the car. Furthermore, the openings provide access to the interior of the side sills to enable the tubes to be welded to the channel and plate members of the side sill.
The side sills are rigidly secured to body bolsters which are fabricated as box beams of thin metal plate to further reduce the weight of the car. The car is provided with container supporting feet secured to the lower portion of the side sills for supporting either two 20-foot or one 40-foot long container in a lower tier; and either a 40-foot or 45-foot container in an upper tier. The car may support a stack of containers having a total height of about 19 feet, and a width of either about 8 feet or 81/2 feet. It is to be understood that the car can be appropriately designed to handle other container lengths such as 45- and 48-foot-long containers in the lower tier and appropriate combinations of containers on the upper tier.